ByClara Moskowitz, SPACE.com Senior WriterMay 26, 2010

Cape Canaveral, Fla. — The Wednesday landing of NASA's space shuttle Atlantis may have capped a successful mission slated to be the spaceship's last trek to space, but the orbiter's immediate future is not yet set in stone. Debate is still underway to determine whether the shuttle should get one more flight or be sent straight to a museum.

As Atlantis' most recent mission demonstrated, the orbiter is in good shape, NASA shuttle officials said today just after the shuttle landed here at the agency's Kennedy Space Center.

"Not only is this mission fantastic, but the entire life of Atlantis, the folks who built it, all the missions it's flown over its career have been just amazing," shuttle launch integration manager Mike Moses said. "I can't even begin to talk about how proud I am of Atlantis and the whole team that put it together."

The shuttle finished a 12-day mission to the International Space Station to deliver a new Russian room and outfit the station with spare parts for the era after NASA's three-orbiter space shuttle fleet retires. Two more shuttle missions are currently planned – one each for Atlantis' sister ships Discovery and Endeavour.

But what about Atlantis?

Whether or not the STS-132 mission will actually be the orbiter's last spaceflight has not been decided. Starting tonight, Atlantis will be processed and refurbished just in case it has to fly again.

The orbiter is on call to serve as the emergency rescue ship to be on reserve in case of a serious problem with NASA's final planned shuttle flight, the STS-134 mission of Endeavour slated for no earlier than late November. If something goes awry on that flight, shuttle Atlantis could be readied to retrieve Endeavour's astronauts from the station and return them back to Earth.

However, NASA and lawmakers are also considering whether to shift this so-called "launch on need" mission to a full-fledged final shuttle flight. The hardware, including an expendable external fuel tank, is already in place to fly one more mission. But that plan would require more funding to retain space shuttle workers for longer than currently planned.

It costs NASA about $200 million a month to keep its space shuttle program running, program managers have said.

One more mission, which NASA would likely launch with a crew of four in June 2011, would allow the agency to stock up on more supplies for the space station since the outpost is slated to continue running through at least 2020. Beyond the shuttle era, the station will be serviced by manned Russian Soyuz vehicles and unmanned Russian, Japanese, European and American commercial cargo-carrying spacecraft.

Eventually, U.S. President Barack Obama and NASA hope private companies can build spaceships to ferry astronauts to the orbiting laboratory, too.

In the meantime, NASA simply doesn't have the funds to continue flying the space shuttle and work on developing next-generation rockets and vehicles at the same time.

"I think we'd all love to have kept flying shuttle while we set up the new system ... we just don't have the budget to do that, and that's the reality of the world we live in," Moses said.

Yet just because the shuttles are headed for retirement doesn't mean they're not in good health and capable of flying at least one more flight, he said.

"It's true they are 30 years old but they are not old at all," Moses said. "They're in fantastic shape, they fly perfectly and they do exactly what we mean them to."

Whenever it finally comes, the retirement of the space shuttle fleet will be a bittersweet time for NASA.

"It's just an amazing machine, and it's a testament to America's prowess in space that we're able to reuse the spacecraft over and over," shuttle launch director Mike Leinbach said. "I'm going to hate to see that go away."